Marcio Donnangelo, Emerson Automation Solutions, USA, discusses how installing wireless transmitters can help refineries to improve operations and reduce the number of unscheduled outages, while being safer and more energy efficient.

ADIGITALECOSYSTEMIMPROVING

REFINERY

MARGINS

KEYNOTE

SERIES

O il refineries operate under a wide range of economic pressures, government regulations, and changing conditions, making it more difficult to maximise refining margins. Refineries are faced with problems such as the

loss of senior personnel to retirement, different crude feedstock, ageing equipment, and a lack of information from various areas of the plant.

For example, many refiners maximise their use of discounted opportunity crude oils, but using this type of feedstock often presents significant processing challenges. Refineries built in the 1960s and 1970s were originally designed to handle a certain type of oil, such as sweet crude. The changing nature of oil being supplied for refining magnifies problems in new and ageing facilities. For example, unit preheat exchangers can foul unpredictably when fed with certain types of crude.

Installing WirelessHART® pressure and temperature transmitters on heat exchanger banks and feeding their measurements to process data analytics software makes it possible to identify problems with heat exchanger fouling. Similar problems can also be identified on many other types of refinery equipment with the transmitters.

Table 1 shows the potential savings in a 250 000 bpd refinery when the transmitters are installed on various equipment and processes, with data analytic software processing the measurements.

The wireless solutionWireless measurement devices using WirelessHART technology are key enablers to implementing a Pervasive SensingTM strategy to monitor anything, anywhere, in the refinery. WirelessHART is an international industrial standard (IEC 62591) self-organising, wireless, mesh network leveraging the well-known and widely used HART protocol. Adding low cost installation of wireless monitoring points throughout the plant provides analysis and alerts personnel to problems. This helps optimise production processes by monitoring the health of pumps, motors, steam straps, pressure relief valves (PRVs), heat exchangers, valves, piping systems, and other equipment.

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The technology is compatible with new and legacy refinery control systems. A Pervasive Sensing solution can be installed, running and improving operations in any refinery in short order.

Previously, additional sensor inputs would have been wired from the sensing point – such as a pump – to a control and monitoring system. Adding this wiring to an existing facility is usually an expensive undertaking, and often requires significant downtime. But wireless transmitters allow points of measurement to be added at a fraction of the cost and time of their wired equivalents. Some are

non-intrusive to the process and can be installed without any downtime.

The initial installation requires a gateway, which interfaces wireless transmitters to an analytics software application, to a historian and/or to the control and monitoring system – leveraging multiple communication protocols to make these connections. Once the first system is installed, it becomes easier to add new wireless transmitters.

Adding new transmitters also makes the network stronger because in a mesh network, every transmitter also works as a repeater, routing the signal along multiple paths as needed to extend the perimeter of coverage and provide alternative paths in case of obstruction. The more wireless transmitters installed in an area, the stronger and more widely spread the network signals (Figure 1).

For example, a major US refinery installed six Rosemount 708 acoustic transmitters on its Butane Bullet relief valves. These devices notify operators if a relief valve is beginning to relieve or leak.

In 2014, the refinery added three Rosemount 848 high-density temperature transmitters on its diesel hydrotreater and combined feed exchangers.

In 2015, the refinery installed a Permasense corrosion monitor and 20 sensors in the refinery’s coker and crude unit. An adapter, which converts a wired transmitter’s 4 – 20 mA output signal to WirelessHART, was added to a meter on a crude feed tank to monitor flow, temperature and API gravity. A wireless vibration monitor was added to the coker jet pumps.

In 2016, the refinery added a high capacity Elite Coriolis Meter with the adapter to its oil movement area for custody transfer of asphalt.

Refinery improvementsThe first step toward refinery improvement is to define new sensing point locations, determine how the new information will be used, and associate the economic values with each pervasive sensing application. Unscheduled outages and production slowdowns classified as mechanical unavailability occur from common problems such as rotating equipment failure, heat exchanger fouling, piping corrosion, and fired equipment constraints.

Energy losses occur from heat exchanger fouling, failed steam traps, and process unit inefficiencies – each of which may go undiscovered from a lack of

complete energy measurements. Refineries understand their macro energy performance through their energy intensity index, but determining exactly where energy is lost is a common challenge when driving an energy improvement programme.

Cooling towersCooling tower instrumentation in many refineries is often old, with many measuring devices out of service. Measurements are difficult because the process environment is corrosive to wiring, mainly due to chemical vapours. As a result, these areas

Table 1. Potential savings in a 250 000 bpd refinery when transmitters are installed

Application Monitoring and analytics

Savings (US$ million)

Implementation cost (US$ million)

ROI (months)

Heat exchanger monitoring

Fouling rate and limits

2.7 – 3.6 0.62 3

Cooling tower monitoring

Efficiency and health

0.3 – 0.5 0.16 4

Steam trap monitoring

Failure 2.5 – 3.3 1.48 5

Relief valve monitoring

Releases and leaks

2.4 – 3.2 1.59 6

Pump monitoring

Cavitation, pump health

0.5 – 0.6 0.55 11

Air-cooled heat exchanger monitoring

Fan health and fouling

0.9 – 1.1 1.2 13

Mobile workforce

Turnaround diagnostics

1.6 – 2.1 0.4 3

Safety shower and eye wash monitoring

Trigger indication

Per incident 0.39 Safety

Total 10.9 – 14.4 6.4 5

Figure 1. If an obstruction is introduced into the network, data will continue to flow because the device already has other established communication paths.

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can be poorly instrumented and controlled. Consequently, monitoring is poor, operations are inefficient, and the towers require a great deal of maintenance and manual operator interaction.

Online measurements are required to provide the data needed to tightly control cooling towers, maintain the assets, and prevent over-maintenance. Automated monitoring also prevents failures, thus limiting downtime in each cooling tower section.

WirelessHART monitoring (Figure 2) offers better control to improve tower efficiency and minimise water consumption. Having the right data enables proper dosing of the cooling tower water to prevent excess chemical use, and to provide the right water chemistry to avoid fouling and damage to the pipes. Proper dosing also improves cooling tower efficiency.

Monitoring cooling towers provides early alerts of bearing, lubrication, or alignment problems in cooling tower fans and pumps. Data analytics software can provide timely alerts for

reverse fan operation in periods of cold weather, and for suggested fan sequencing for optimal power consumption. Data analytics can also provide recommended blowdown and make-up flows to help minimise chemical and water costs.

Steam trapsWhen a steam trap fails to shut, it no longer passes steam and will no longer remove water, air or other gases from the steam system. When a steam trap fails in the open or blow-through condition, it constantly passes steam, meaning despite the internal orifice limiting the amount of steam loss, the amount lost can still be significant.

Steam trap monitoring (Figure 3) reduces water hammer incidents, detects traps that have failed open or failed closed, and eliminates the need for manual rounds and foot traffic in high risk areas. Monitoring also reduces equipment damage caused by water hammer, impingement and corrosion.

Relief valvesMonitoring relief valves, rupture discs, and other pressure relief devices provides immediate notification of a release. New US Environmental Protection Agency (EPA) and other regulations now require monitoring of relief valves and rupture discs. Time-stamped alerts allow a refinery to conduct root cause analyses to avoid future releases. As with steam traps, wireless monitoring safely collects data without manual rounds, keeping employees out of hazardous areas or remote locations.

In addition to potential environmental and safety concerns, process upsets causing overpressures can affect production and uptime, negatively impacting profitability. A relief valve is sometimes the only indicator of process upsets, so the sooner an event can be detected, the quicker operators can respond to the root cause.

Historically, relief valves have been difficult to monitor because of their hard-to-access locations Monitoring methods typically include the manual inspection of tell-tale signs. For example, wind socks are often used to monitor releases to the atmosphere.

A reliable, effective and economic way to monitor relief valves and rupture discs is to use non-intrusive acoustic transmitters. Process fluid flowing through valves and orifices generates acoustic waves in a wide and complex range of frequencies and magnitudes. Acoustic transmitters detect ultrasound acoustic waves in the pipe wall as well as its temperature. These devices are wireless, small, lightweight, and non-intrusive. They can be easily clamped on the exhaust pipe with no required process penetrations or downtime (Figure 4).

PumpsThe online monitoring of pumps through the addition of wireless measurement of vibration, pressure, and seal fluid levels allows for the early detection of excessive vibration, cavitation, and seal failure problems. Maintenance can be notified of pending problems, leading to improved production through fewer unscheduled outages.

For example, 10 – 15 LPG pumps in a refinery are typically checked manually once a month for vibration, and bad actors are checked once a week. With ever-changing process conditions, infrequent spot inspections are insufficient to detect pump problems and seal failures. Hydrocarbon leaks

Figure 2. An enclosure protects WirelessHART transmitters from the corrosive environment near cooling towers.

Figure 3. Rosemont 708 wireless acoustic transmitter detects steam trap problems.

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are possible due to seal failures, which can lead to production losses, fires and safety incidents. If a pump fails and seals break in an LPG area, this presents a high risk of explosion. A refinery can see a US$100 000 insurance premium risk reduction by adding automated monitoring to process pumps.

The digital ecosystem for IIoTA refinery employing wired and wireless transmitters, gateways and analysis software creates an Industrial Internet of Things (IIoT) ‘digital ecosystem’ within the entire complex. For example, Emerson’s Plantweb Digital Ecosystem (Figure 5) using a Pervasive Sensing portfolio of wired and WirelessHART transmitters is a digital ecosystem. These devices send reliable real-time data through secure communication to appropriate experts, application software, or to remote connected services – turning the data into actionable information, which can be sent to anyone, anywhere.

ConclusionA typical 250 000 bpd refinery has hundreds, if not thousands, of unmonitored processes, devices and systems susceptible to unplanned failures or degraded operations. These conditions can waste energy, increase the probability of safety issues, and escalate repair costs – potentially shutting down processes or an entire refinery.

A ‘digital ecosystem’ strategy using wireless sensors to monitor equipment, detect problems, and alert operations personnel can save a refinery millions of dollars every year in maintenance and energy costs. These solutions can also improve safety, prevent releases that could result in fines and penalties, and extend the life of expensive process equipment.

Figure 5. An example of a digital ecosystem.

Figure 4. A wireless relief valve monitor simply clamps on to the pipe downstream of the valve.